1. Field of the Invention
The invention relates to thin film magnetic transducers and in particular to a method and means of protecting magnetoresistive (MR) heads from damage caused by electrostatic discharge (ESD) during manufacture.
2. Description of the Related Art
Presently known thin film magnetic heads include an inductive write element for recording signals and a magnetoresistive (MR) sensor for reading the recorded signals. Write operations are carried out inductively using a pair of magnetic write poles which form a magnetic path and define a transducing nonmagnetic gap in the pole tip region. The transducing gap is positioned close to the surface of an adjacent magnetic recording medium such as a rotating magnetic disk. An electrical coil formed between the poles causes flux flow in the magnetic path of the poles in response to a current in the coil that is representative of information to be recorded.
Read operations are carried out by a magnetoresistive (MR) sensor which is spaced from a pair of magnetic shields. The MR sensor changes resistance in response to changes in magnetic flux on the adjacent magnetic recording medium. A sensing electric current passed through the MR sensor responds to the resistance of the MR sensor, which changes in proportion to changes in the magnetic flux. Conventionally, the MR sensor is electrically isolated from the pair of magnetic shields, and a separate set of conductors are provided on one surface of the MR sensor to pass a reference current through the MR sensor.
Compared to conventional thin film recording heads, MR heads are up to 100 times more susceptible to damage during manufacture caused by electrostatic discharge (ESD). During manufacture, the disk drive elements are open to the environment and subject to possible static discharge from human handling. In contrast, during operation of the disk drive in a computer, the elements are encased in a protective cover with appropriate protections against ESD.
One prior approach to protection from ESD damage is described in U.S. Pat. No. 5,644,454 "Electrostatic discharge protection system for MR heads" of Satya P. Arya, et al. which was granted to IBM on Jul. 1, 1997. This patent describes an MR head which receives ESD protection from a mechanism that automatically shorts the MR head whenever a suspension assembly on which the head is mounted is not installed in a head disk assembly (HDA). The suspension assembly includes a flexure underlying a load beam, which is connected to an actuator arm. The MR head is mounted to a distal end of the flexure. Leads from components of the MR head are brought out in the form of MR wired leads running along the load beam and the support arm to a nearby terminal connecting side tab. The conductors are separated and exposed at a designated point along the flexure to provide a contact region. A shorting bar, which comprises an electrically conductive member attached to the actuator arm, automatically shorts the MR wired leads at the contact region when absence of support for the MR head permits the load beam to bend sufficiently toward the shorting bar. Thus, when the assembly is removed from installation in an HDA, the flexure is permitted to move toward the shorting bar, bringing the contact region and the shorting bar in electrical contact to short the MR wired leads and thereby disable the MR sensor. When the assembly is installed in an HDA, the MR head is supported by an air bearing or the disk itself, depending upon whether the disk is rotating or stopped, respectively. In either case, the load beam is not permitted to sag while the shorting bar contacts the conductors, thus deactivating the MR sensor. Temporary ESD protection mechanisms are also provided, these being removable prior to operation of the HDA by breaking and removing various temporary shorting mechanisms.
The disadvantage of this approach is that the structure is complex to manufacture and adds height to the head stack assembly. The temporary ESD protection mechanisms are removed prior to operation of the HDA by breaking and removing various temporary shorting mechanisms, and do not provide a means for replacing the shorting mechanism after testing during manufacture, Therefore the shorting mechanisms are not reusable.
It is an object of this invention to provide an ESD protection mechanism that can be temporarily removed for testing during manufacture and is reusable.
It is an object of this invention to provide a protection mechanism used with a flexure for shorting the MR wired leads to disable the MR sensor and isolate it from electrostatic discharge.
It is a further object of this invention to provide a test clip for use with a temporary ESD protection mechanism for testing an MR head during manufacture.